Photochromic polymers, that is, polymers which contain photochromic groups in a macromolecule, are materials of significant technological potential in many industrial fields. For example, such polymers can be used in the manufacture of the plastic material of eye lenses and the manufacture of windows for the automobile industry.
Spirooxazines and their use in photochromic lenses have been recently reviewed by Crano et al..sup.1 There has also been a significant amount of research reported on a number of side-chain photochromic polymers in which photochromic spiropyran or spirooxazine side groups are attached to a main chain through a flexible spacer.sup.2-6. The structure of these compounds allows incorporation of a very high content of a photochrome in a polymer which can reach 100%. That is, each structural unit of the polymer contains the photochromic group. Properties of such polymers can be substantially different from the properties of the polymers containing photochromic molecules as solute, as photochromic compounds have been usually employed in photochromic lenses. Such solutions in polymers have inherent restrictions in solubility of the photochromic compound.
Liquid crystalline polyacrylates and polysiloxanes containing different photochromic spironaphthooxazine side groups were recently reported.sup.6. A two-step reaction was described therein for the synthesis of the liquid crystalline polysiloxane polymers containing spiroindolinenaphthooxazine side groups. First, the siloxane polymer was reacted with a mixture of a mesogen, such as p-cyanophenylbenzoate, and an active ester that contains an olefinic terminal group. Then the spironaphthooxazine photochromic groups was incorporated into the active ester-mesogen copolymer by reaction of the copolymer with 5-amino-spiroindolinenaphthooxazine, resulting in photochromic liquid crystal polysiloxanes comprising also mesogenic groups.
The aforementioned synthesis was effective but includes several limitations. Most significantly, the reaction of the photochromic monomer with the active ester side groups could not go to completion because several of the ester groups were hydrolyzed to free acid groups, which influence the photochrome kinetics thereby slowing the change of color rates.
The present invention provides a variety of new photochromic amorphous polysiloxanes with spironaphthooxazine side groups and a novel single-step synthetic method used for the incorporation of the spirooxazine in the polymer macromolecules. The present invention provides a one-step synthesis which avoids the use of active ester side chain polymers thereby providing a high amount of incorporation of photochromic groups per --Si--H moiety while not having the prior art limitations presented by the active ester groups forming into free acid sites.